Field of the Invention
This invention describes thermally insulative aerogel-containing foam compositions, a composite insulation which these compositions can provide, and their preparation.
Thermal insulation is an important and valuable product. Although many insulative compositions are already in use, there is a continuing desire for energy conservation pushing a drive to achieve insulation having lower thermal conductivity (T.sup.k).
In addition to a low T.sup.k, furthermore, insulation ideally should have other qualities. Low flammability and low smoke are particularly important for use in both business and residential structures. It should also be easily prepared, non-toxic, environmentally safe in both use and preparation, and it should have good handling properties. Insulation which is capable of being molded into large sheets or other needed shapes, and which has sufficient flexibility and compressibility to be transported, handled and installed in homes, buildings, and even manufactured goods is called for.
Present forms of thermal insulation include foams. Foams which require blowing agents, however, can be detrimental to the environment and difficult to make. The foamed insulation also can have the disadvantage of the flammability of the foam itself, and frequently the added problem of toxic smoke even with, and sometimes because of added flame retardants.
Aerogels are known to be advantageously insulative; but, as insulation, they are disadvantageous in several ways. As a loose fill, aerogel is dusty, and is prone to settling over time. In addition to this, the aerogel is brittle, non-flexible and when compressed it fractures. As a result, aerogel can't be flexed during use. An attempt to compress or flex large pieces of it will result in breaking them. Transportation, handling and installation are difficult with aerogels due to the lack of shock resistance and flexibility.
Thus, there is need for the thermally insulative composites which are described herein. The present invention provides thermal insulation having a low T.sup.k, good handling properties, fire resistance, low smoke, and which is also environmentally safe and is easily made.